On Fri, Mar 23, 2018 at 3:15 AM, Alexander Motin <m...@freebsd.org> wrote:
> Author: mav > Date: Fri Mar 23 02:15:05 2018 > New Revision: 331404 > URL: https://svnweb.freebsd.org/changeset/base/331404 > > Log: > MFV r331400: 8484 Implement aggregate sum and use for arc counters > > In pursuit of improving performance on multi-core systems, we should > implements fanned out counters and use them to improve the performance of > some of the arc statistics. These stats are updated extremely frequently, > and can consume a significant amount of CPU time. > > > > Due to seriously fat locks this struct: typedef struct aggsum_bucket { kmutex_t asc_lock; int64_t asc_delta; uint64_t asc_borrowed; uint64_t asc_pad[4]; /* pad out to cache line (64 bytes) */ } aggsum_bucket_t __aligned(CACHE_LINE_SIZE); ends up using *two* cache lines. Without asc_pad the size is 48 bytes. asc_pad adds 4 * 8 = 32 which pushes it to the next line for no good reason. That said, I suggest #ifndefing it the field. -- Mateusz Guzik <mjguzik gmail.com> _______________________________________________ svn-src-all@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/svn-src-all To unsubscribe, send any mail to "svn-src-all-unsubscr...@freebsd.org"
